Efficacy of immune checkpoint inhibitors in patients with KRAS-mutant advanced non-small cell lung cancer: A retrospective analysis

Abstract The efficacy of immune checkpoint inhibitors (ICIs) on KRAS-mutant advanced non-small cell lung cancer (NSCLC) remains controversial. This retrospective study compared the effects of ICIs treatment and chemotherapy on the prognosis of patients with KRAS-mutant advanced NSCLC and different mutant subtypes in the real world. The study included 95 patients with KRAS-mutant advanced NSCLC. Patients treated with first-line ICIs plus platinum-containing chemotherapy had better progression-free survival (PFS) (7.4 vs 4.5 months, P = 0.035) and overall survival (OS) (24.1 vs 13.2 months, P = 0.007) than those receiving platinum-containing chemotherapy alone, and second-line ICI monotherapy was associated with better PFS (4.8 vs 3.0 months, P = 0.043) and OS (18.0 vs 13.8 months, P = 0.013) than chemotherapy monotherapy. There was no significant difference in PFS (5.267 vs 6.734 months, P = 0.969) and OS (19.933 vs 20.933 months, P = 0.808) between patients with KRAS-mutant and KRAS-wild-type NSCLC treated with ICIs or between KRAS G12C and KRAS non-G12C patients (PFS: 8.1 vs 4.8 months, P = 0.307; OS: 21.3 vs 21.8 months, P = 0.434). In summary, patients with advanced NSCLC with KRAS mutations can benefit from ICIs, but no difference between KRAS mutant subtypes was observed.


Introduction
Lung cancer incidence and mortality rates are among the highest of all malignancies worldwide [1], and non-small cell lung cancer (NSCLC) accounts for 85% of all lung cancers. Kirsten rat sarcoma viral oncogene homolog (KRAS) is one of the most commonly mutated oncogenes in NSCLC, with a mutation incidence of approximately 25% in Western populations [2]; however, the incidence of KRAS mutation in adenocarcinoma in the Asian population is 5-15% [3]. For a long time, the standard treatment for KRAS-mutant NSCLC patients has been cytotoxic chemotherapy. The emergence of tyrosine kinase inhibitors targeting epithelial growth factor receptor (EGFR) mutations marked the beginning of the era of precision medicine [4]. The KRAS protein lacks a suitable "pocket" for small-molecule binding, making it difficult to develop effective drugs against KRAS [5]. The inhibitors AMG 510 and MRTX849 targeting the KRAS G12C mutation have shown promise in early clinical trials [6,7]. However, the use of KRAS G12C inhibitors in the treatment of NSCLC is limited in the real world.
The development of immune checkpoint inhibitors (ICIs) profoundly changed the management of lung cancer, and in the past 5 years, ICIs have become the standard treatment for advanced NSCLC [8]. However, the efficacy of ICIs for NSCLC with known carcinogenic drivers is controversial [9][10][11]. The limited data on the efficacy of ICIs in patients with KRASmutant NSCLC are derived from subgroup analyses of large clinical studies. In addition, the effect of ICIs on KRAS mutant subtypes is rarely reported. Here, we designed a retrospective study to explore the efficacy of ICIs and the prognosis of patients with advanced NSCLC with KRAS mutation treated with ICIs in the real world. We also analyzed the differences in the efficacy of ICIs among KRAS mutant subtypes.

Study design
Patients with advanced KRAS-mutated NSCLC were grouped according to the number of lines of treatment and regimen. The first-line treatment was ICIs plus platinum-containing chemotherapy or platinum-containing chemotherapy alone, and the second-line treatment was ICI monotherapy or chemotherapy alone. All chemotherapy and ICI regimens were administered according to the standard doses established by the National Comprehensive Cancer Network guidelines.

Study population and selection criteria
Patients who were diagnosed with NSCLC in Zhejiang Cancer Hospital between March 2015 and March 2021 were retrospectively analyzed. The diagnosis of KRASmutant NSCLC was confirmed by real-time PCR or next generation sequencing. The enrolled patients met the following selection criteria: (1) patients diagnosed as NSCLC by pathology, and the histological classification of NSCLC was based on the World Health Organization criteria (2015 version) [12], (2) presence of KRAS mutations, and (3) complete data of baseline clinicopathological characteristics including age at diagnosis, gender, smoking history, histology, Eastern Cooperative Oncology Group performance status (ECOG PS) score, intrathoracic metastasis status, liver metastasis status, bone metastasis status, brain metastasis status, and KRAS mutation subtypes. Exclusion criteria were as follows: (1) other malignant disease histories at the time of diagnosis (because of the difficulty in calculating recurrent events and because double cancers may increase the risk of recurrence), (2) positive for EGFR, ALK, MET, ROS1, HER2, BRAF, RET, and NTRK, and (3) ECOG PS score of 3-4. In addition, we collected 58 patients with KRAS-wild-type advanced NSCLC treated with ICIs in our hospital during the same period who were matched according to the basic characteristics of KRAS-mutant patients.
Ethics approval: This study was approved by the Chinese Academy of Sciences University Cancer Hospital (Zhejiang Cancer Hospital) Ethics Committee (IRB-2022-33) and individual consent for this retrospective analysis was waived.

Consent:
As this was a retrospective study, patient consent was waived, and anonymity was ensured.

Data collection
The medical records of patients with KRAS-mutant and KRAS-wild-type advanced NSCLC were collected, and baseline clinicopathological characteristics, treatment, and follow-up were recorded. Patient follow-up information was obtained from the last clinical visits, follow-up registration records, and follow-up phone records. The deadline for follow-up was December 31, 2021.

Assessments
Response to treatment was assessed using the Response Evaluation Criteria in Solid Tumors (RECIST) v1.1. Prior to analysis, efficacy was examined by two oncologists, who evaluated the tumor response according to RECIST 1.1 via chest computed tomography and/or brain magnetic resonance imaging every 4-8 weeks. Objective response rate (ORR) was defined as the proportion of patients with complete response plus partial response (PR). Progression-free survival (PFS) was defined as systemic progression or death from the date of initial treatment, or the date and time of the last follow-up, whichever comes first triggers the date review of the event. Overall survival (OS) was defined as the time from the diagnosis of advanced NSCLC to death or the last follow-up.

Efficacy
Of 58 KRAS-wild-type patients treated with ICIs, 16  Patients treated with ICIs plus chemotherapy had a better mPFS than those receiving chemotherapy alone (7.4 vs 4.5 months, P = 0.035, Figure 1b). For second-line therapy, the ICI monotherapy group had an ORR of 24% and DCR of 64%, whereas the chemotherapy monotherapy group had an ORR of 0% and DCR of 70%. Similarly, patients receiving ICI monotherapy had a better mPFS than those receiving chemotherapy monotherapy (4.8 vs 3.0 months, P = 0.043, Figure 1c).

Discussion
This retrospective study explored the response to treatment and prognosis of patients with KRAS-mutant NSCLC who received ICIs with or without combination chemotherapy as firstor second-line treatments compared with chemotherapy alone, compared with published clinical studies of NSCLC patients who received ICIs. There are no published prospective clinical studies of patients with KRAS-mutated NSCLC who received ICIs, and the existing literature is limited to subgroup analyses or meta-analyses of large clinical studies. The findings of the present study show that PFS and OS were significantly prolonged by ICIs with or without chemotherapy compared with chemotherapy combination or monotherapy as firstand second-line treatments.
Several studies have evaluated the efficacy of ICIs in patients with advanced KRAS-mutant NSCLC, although  Given the heterogeneity of KRAS mutations, KRAS G12 status was divided into G12C and non-G12C. Studies suggest that KRAS G12 status is not related to the efficacy of ICIs [19][20][21][22]. However, in a retrospective analysis that included 168 KRAS G12C and 219 KRAS non-G12C patients with advanced NSCLC treated with ICIs, ORR, PFS, and OS were better in patients with KRAS G12C mutations. In the present study [23], the efficacy of ICIs did not differ significantly between KRAS G12C and non-G12C patients regarding PFS (8.1 vs 4.8 months, P = 0.307) and OS (21.3 vs 21.8 months, P = 0.434).
In addition to the KRAS mutation subtypes, co-mutation plays an important role in the efficacy of ICIs. Comutation of KEAP1/NFE2L2 with KRAS is associated with poorer ICIs efficacy [2]. Furthermore, the KRAS gene is associated with a high tumor mutational burden, CD8+ tumor cell infiltration, and high programmed death ligand 1 expression, which may be associated with better efficacy of ICIs [15].
The present study had several limitations. First, the retrospective nature of the study may have affected the results. Second, information on KRAS-mutant subtypes and co-mutation genes was not available for all patients. In addition, the choice of drugs for ICIs and chemotherapy was not uniform, and the related data were thus different. Finally, the sample size was relatively small; prospective or larger sample size studies are needed to validate the results.

Conclusions
Patients with advanced NSCLC with KRAS mutations can benefit from ICIs, although no difference between KRAS mutant subtypes was observed.